German Patent No. 2 165 942 describes two embodiments of a circuit breaker. In one embodiment, the circuit breaker can be inserted into and withdrawn from the cubicle of a switchgear by a rectilinear traveling motion, the joint between the arc quenching chamber and the blow-out attenuator being arranged at an angle to the moving direction to achieve a wedge-type interaction.
In the other of the two embodiments, the circuit breaker has an approximately cylindrical housing and can be inserted into the switchgear by a rotary motion. In the course of the rotary motion, the mouth surface of the arc quenching chamber and the sealing surface of the blow-out attenuator engage with one another.
The purpose of the blow-out attenuator is to affect the switching gases emerging during the switching of the circuit breaker in such a way that they exhibit electrically neutral properties, thereby avoiding the requirement for a safety clearance between the mouth of the blow-out attenuator and live or grounded parts.
It is essential for the desired functioning of the described arrangement that the blow-out attenuator reliably engage with the arc quenching chamber when inserting the circuit breaker into its operating position to avoid leakage, thereby preventing switching gases from escaping at the joint between the arc quenching chamber and the blow-out attenuator. It is also necessary to ensure a sufficient resistance to the switching-gas pressure, to be able to make full use of the switching capacity of the circuit breaker.